The present invention relates to yeast for enhancing expression of a gene and a method for preparing a protein thereby.
Many studies have recently been conducted for producing useful proteins by yeast, using genetic engineering techniques. The reason is that expression of some genes which had been impossible in a prokaryote such as Escherichia coli became possible in yeast, a eukaryote. One example thereof is the expression of hepatitis B virus surface antigen having immunogenicity. When proteins having many disulfide bonds such as human lysozyme are produced, inactive types of human lysozyme are expressed intracellularly or secreted in expression using Escherichia coli or Bacillus subtilis. However, an active type of human lysozyme is expressed and secreted by yeast [K. Yoshimura et al., Biochem. Biophys. Res. Commun. 145, 712 (1987)].
However, the amounts of foreign genes expressed by yeast are generally lower than those expressed by Escherichia coli. Therefore, it is very important for industrial production of foreign proteins to increase the gene expression in yeast.